1. Field of the Invention
The present invention relates to a wire spacing device which protectively keeps two wires of a wire harness at a predetermined distance, and is particularly suited for protecting electric wires from interference signals, such as electromagnetic waves.
2. Description of the Prior Art
In FIG. 19, a conventional wire harness 101 constructed in such a manner such that a plurality of electric wires 102 are bundled and then are wrapped therearound by a tape 103 as shown. Since the electric wires 102 are bundled together by wrapping, a distance between any two wires 102 easily varies during or after installation of the wire harness 101 in equipment. Therefore, even if a specific pair of wires 102 are separated at a certain distance before wrapping the tape 103 to construct the wire harness 101, they may come close to each other after the installation.
When a high power line is passing adjacent to a signal line, the electromagnetic field generated by the high power line tends to interfere with the signal line's reception of desired signals. For example, a signal line such as a speaker line 104 for connecting the speaker (not shown) and the amplifier (not shown) should be held away from the power line 105 to prevent the speaker line from receiving the strong electromagnetic field generated by the power line 105. When the speaker line receives the electromagnetic field of the power line 105, noise signals will be added to the speaker lines 104, resulting in a degradation of sound produced by the speaker.
Since these two lines 104 and 105 may come close to each other, as described above, in the conventional wire harness 101, one way to avoid the electromagnetic interference is to shield the signal line, but results in high manufacturing cost.
In FIG. 20, the conventional wire harness 101 accommodated in a protection box 201 for protecting the wire harness 101 from the external effect is shown. The protection box 201 is closed by a lid 204 with the wire harness 101 accommodated therein and is located, e.g., on the floor of the automobiles. Thus, the wire harness 101 inside the protection box 201 can be protected from various the violent stresses from outside. It is also possible to protect the wire harness 101 from the effect of an electromagnetic field from outside when the protection box 201 is made of an electrically shielding material such as metal. However, it is not possible to protect the speaker lines 104 from the electromagnetic field of the power line 105, as described above. To avoid the mutual interference between the wires in the harness 101, it is necessary to shield the wires itself or use the shield wires to protect from the interference by the electromagnetic field from other lines, resulting in the large wire size and the increase of manufacturing cost.
As shown in FIG. 21, to prevent such electromagnetic effect, a split type wire spacing device 210 is proposed, such as described in the Japanese Laid-open Patent Publication No. 63-28213, published Feb. 5, 1988. The split type wire spacing device 210 has an upper unit 217A and a lower unit 217B which are made of an electrically shielding material such as metal. A plurality of spacing walls 218 are formed on the inside surface of the upper and lower units 217A and 217B so that a plurality of wire recesses 219 are formed therein. In this device 210, when one of two electrical wires 102 interferes with the other, the two wires 102 are separately placed in the different recesses 219. It is possible to prevent one wire from being interfered with the other wire without using any electric shield to the wires, because the spacing device 210 is made of an electrically shielding material. However, the wire spacing device 210 is heavy because it is made of metal. Furthermore it is difficult to form the spacing device 210 in a desired configuration, without greatly increasing the manufacturing cost.